As a history buff, Modern Marvels is a very good show to watch. It's certainly become a personal favorite over the years.
One of the the things I enjoy most is the wide range of topics. You can expect to see shows dedicated to everything from the Great Wall of China and plastics to rubber and commercial fishing. With an hour to dedicate to a particular subject, they offer a great wealth of information, going back to the earliest inception of any given technology or industry.
With so many episodes in the vault, there are only so many more topics to cover, and for this reason, the show's beginning to go downhill. The quality is still there, but the future is so-so. They could opt to re-edit some episodes and update them as things advance.